Poor cold flow properties of vegetable oils are a major problem preventing the
usage of many abundantly available vegetable oils as base stocks for industrial lubricants.
The major objective of this research is to improve the cold flow properties of vegetable
oils by various techniques like additive addition and different chemical modification
processes. Conventional procedure for determining pour point is ASTM D97 method. ASTM
D97 method is time consuming and reproducibility of pour point temperatures is poor
between laboratories. Differential Scanning Calorimetry (DSC) is a fast, accurate and
reproducible method to analyze the thermal activities during cooling/heating of oil. In
this work coconut oil has been chosen as representative vegetable oil for the analysis and
improvement cold flow properties since it is abundantly available in the tropics and has a
very high pour point of 24 °C. DSC is used for the analysis of unmodified and modified
vegetable oil. The modified oils (with acceptable pour points) were then
subjected to different tests for the valuation of important lubricant properties such as
viscometric, tribological (friction and wear properties), oxidative and corrosion
properties.A commercial polymethacrylate based PPD was added in different percentages and the pour points
were determined in each case. Styrenated phenol(SP) was added in different
concentration to coconut oil and each solution was subjected to ASTM D97 test and
analysis by DSC. Refined
coconut oil and other oils like castor oil, sunflower oil and keranja oil were mixed in
different proportions and interesterification procedure was carried out. Interesterification
of coconut oil with other vegetable oils was not found to be effective in lowering the pour
point of coconut oil as the reduction attained was only to the extent of 2 to 3 °C.Chemical modification by acid catalysed condensation reaction with coconut oil
castor oil mixture resulted in significant reduction of pour point (from 24 ºC to -3 ºC).
Instead of using triacylglycerols, when their fatty acid derivatives (lauric acid- the major
fatty acid content of coconut oil and oleic acid- the major fatty acid constituents of monoand
poly- unsaturated vegetable oils like olive oil, sunflower oil etc.) were used for the
synthesis , the pour point could be brought down to -42 ºC. FTIR and NMR spectroscopy
confirmed the ester structure of the product which is fundamental to the biodegradability
of vegetable oils. The tribological performance of the synthesised product with a suitable AW/EP
additive was comparable to the commercial SAE20W30 oil. The viscometric properties
(viscosity and viscosity index) were also (with out additives) comparable to commercial
lubricants. The TGA experiment confirmed the better oxidative performance of the
product compared to vegetable oils. The sample passed corrosion test as per ASTM D130
method.